1. Field of the Invention
The present invention relates to an inkjet print apparatus and inkjet printing method that eject ink from a plurality of ejection ports onto a printing medium to thereby perform printing. More particularly, the present invention relates to preliminary ejection on a printing medium that, in order to maintain a stable ejection state from the plurality of ejection ports, performs ejection irrelevant to any image toward the printing medium in printing.
2. Description of the Related Art
An inkjet print apparatus ejects ink from an individual printing element depending on the image data to print a desired image on a printing medium. In such an inkjet print apparatus, along with evaporation of ink from an ejection port, the ink inside the printing element is increased in viscosity or fixed. Therefore a printing element having a low ejection frequency ejects ink that is denser than necessary, or it cannot perform normal ejection. Even in the printing element in which the increasing in viscosity or fixing occurs, if ejection is performed several times, a dot density or ejection state can be restored. However, the increasing in viscosity or fixing proceeds along within a period of time during which ink is not ejected (non-ejection period), and therefore the number of ejections necessary for restoring to normal ejection is also increased as the non-ejection period increases (see FIG. 12). For this reason, in an individual printing element, it is desirable to perform ejection at a certain level of frequency.
However, the ejecting operation of each printing element depends on the image data, and therefore only with printing an actual image, it is difficult to maintain a desired ejection frequency in all printing elements. Accordingly, in many inkjet print apparatuses, by appropriately performing ejection irrelevant to image data (so-called preliminary ejection), the ejection state is stabilized in all printing elements.
In recent years, as large-sized printing has widely spread and printing elements are ejecting smaller droplets, even during printing on a sheet of printing medium, the preliminary ejection may be required. At this time, in the case of, for example, a serial type inkjet print apparatus, a carriage can be moved for every main scanning to a position away from the printing medium to perform the preliminary ejection into a cap that is prepared in advance. However, in the case of a full-line type print apparatus to which a printing head is fixed, the printing head cannot be moved away from the printing medium until the completion of printing on a sheet of printing medium.
In order to deal with such a problem, for example, Japanese Patent Laid-Open No. 2009-255180 discloses a method for, in a full-line type inkjet print apparatus, performing preliminary ink ejection to the extent that the preliminary ejection does not stand out on the sheet of printing medium printed with the image (so-called preliminary ejection on printing medium). If the method disclosed in Japanese Patent Laid-Open. No. 2009-255480 is employed, the preliminary ejection can be performed during printing of an image, so that the extension of the printing time for performing the preliminary ejection irrelevant to the image can be eliminated, and quick printing on a large-sized printing medium can be performed in a stable ejection state.
The inkjet print apparatus is provided with a mode in which, in order to maintain high quality image output, various test patterns are printed at arbitrary timings to check printing states of printing heads. Also, by making corrections of printing data on the basis of the result of reading the test patterns by using the naked eye or sensor, image defects occurring along with an ejection variation among the printing heads or an error of the print apparatus can be reduced.
Meanwhile, even during the printing of such test patterns, evaporation of ink from the printing element that has not performed ejection for a while proceeds, and therefore even during the printing of the test patterns, the ejection state of the printing element may become unstable. Accordingly, if an ejection state of an individual printing element is taken into consideration, even during the printing of the test patterns, it is desirable to perform the preliminary ejection on printing medium. However, depending on the type or purpose of the test pattern, it may not be preferable to print a dot irrelevant to the pattern during printing of the test pattern. This is because if an irrelevant dot is printed by the preliminary ejection within the test pattern, information to be read from the pattern cannot be accurately detected, and even if various corrections are made according to the obtained information, image quality may not be improved. Thus, when the test pattern is printed, it is difficult to print the test pattern with high reliability while stabilizing the ejection state of printing elements. Japanese Patent Laid-Open No. 2009-255480 also describes the method for performing the preliminary ejection on printing medium while printing an actual image, but does not deal with the preliminary ejection on printing medium in the case of printing a test pattern as described above, at all.